The present invention relates to a fail-safe processing system and method for internal combustion engines with an electronic-controlled intake device and a variable valve-lift mechanism for controlling a lift amount of valves.
An exemplary fail-safe processing system for internal combustion engines is constructed to stop an engine in the event that the electronic-controlled intake device fails or fixes with an air amount sufficiently secured for vehicle acceleration. Specifically, when detecting a failure of the electronic-controlled intake device which can make fine restriction of engine output torque impossible to cause vehicle acceleration or the like contrary to drivers intention, the system stops engine operation by fuel cut, etc.
In the above fail-safe processing system, however, since the system carries out fuel cut and then stops engine operation when it is determined that a failure of the electronic-controlled intake device occurs with the vehicle being ready for acceleration, the following problem arises. In the event of failure of the electronic-controlled intake device at the time of vehicle acceleration during expressway cruising or passing, the vehicle causes abrupt deceleration, which can bring a driver and passengers into insecure conditions. Moreover, due to inability to run by itself, the vehicle cannot evacuate to safety.
It is, therefore, an object of the present invention to provide a fail-safe processing system and method for internal combustion engines, which when a failure of an electronic-controlled intake device or a variable valve-lift mechanism occurs with a vehicle being ready for acceleration, allows driver""s recognition of this occurrence, avoiding of vehicle acceleration or deceleration contrary to his intention, and continuous vehicle running for evacuation to safety.
The present invention provides generally a fail-safe processing method for an internal combustion engine, the engine including at least an electronic-controlled intake device and a variable valve-lift mechanism for controlling a valve-lift amount, the method comprising:
carrying out a failure diagnosis for determining whether a failure of the electronic-controlled intake device occurs;
determining whether a mode of the failure of the electronic-controlled intake device is a vehicle accelerating mode when it is determined that the failure occurs;
carrying out a fail-safe processing when it is determined that the failure mode is the vehicle accelerating mode, wherein the fail-safe processing determines an optimal value of the valve-lift amount; and
controlling the variable valve-lift mechanism in accordance with the optimal value of the valve-lift amount.